The present disclosure relates to an instant trip apparatus of a molded case circuit breaker, and more particularly, to an instant trip apparatus of a molded case circuit breaker, which is capable of preventing a magnet and an armature from being fused with each other to secure reliability in effective instant trip operation.
A molded case circuit breaker may be electric equipment that breaks abnormal current, i.e., overcurrent, fault current, or short-circuit current between a power and a load when the abnormal current occurs to protect the load and a circuit.
The molded case circuit breaker may have a trip function in which, when the abnormal current occurs, the molded case circuit breaker detects the abnormal current therein to automatically break the abnormal current.
The trip function may be classified into temporary trip and instant trip. In the temporary trip, a circuit breaking operation may be performed after a predetermined time elapses when the abnormal current occurs. Unlike the temporary trip, in the instant trip, the circuit breaker may detect relatively large accident current to break the circuit in the short time.
The trip operation of the molded case circuit breaker with respect to the accident current may be performed for a predetermined time (for example, about 10 mille seconds) by detecting current when circuit current flowing through the molded case circuit breaker is instantaneously applied at a predetermined multiplying factor (e.g., about 200%, about 300%, about 1,000%, about 2,000%, etc.) than rated current.
A mechanism for performing the instant trip may be called an instant trip apparatus.
An instant trip operation will be described through the instant trip apparatus of the molded case circuit breaker according to the related art.
FIG. 1 is a view of an instant trip apparatus of a molded case circuit breaker according to the related art, and FIG. 2 is a view illustrating an instant trip operation in the instant trip apparatus of the molded case circuit breaker according to the related art.
Referring to FIG. 1, the instant trip apparatus of the molded case circuit breaker according to the related art includes a case 10, a heater 11, a bimetal 12, a crossbar 51, a magnet 20, and armature 31.
The heater 11 is installed in the case 10. The heater 11 may enable current to be transmitted therethrough, have uniform resistance, and generate heat according to an amount of flowing current.
The bimetal 12 is installed in the case 10. When current flowing through the heater 11 is over rated current (overcurrent), the bimetal 12 is bent by the generated heat to push the crossbar 51 so that the crossbar 51 rotates to a trip position.
The crossbar 51 may rotate in a left/right direction between the trip position and a normal position according to the rotation operation and also return to the normal position by elastic restoring force of a crossbar spring 52 installed at a rotation center.
Here, in the normal position, the crossbar 51 may have an upper end spaced apart from one side of an upper end of the bimetal 12 and a lower end extending downward.
The magnet 20 is installed in the case 10 to face armature 20. The magnet 20 is electrically connected to the circuit to generate magnetic attractive force when the accident current occurs.
The armature 31 is installed in the case 10 to face one surface of the magnet 20. A lower end of the armature 31 is rotatably supported by a support 32 to horizontally rotate.
The armature 31 is rotatable between a position at which the armature 31 contacts the magnet 20 and a position at which the armature 31 is spaced apart from the magnet 20.
The armature 31 is formed of a material containing iron. When the magnetic attractive force is generated by the magnet 20, the armature 31 rotates to contact one surface of the magnet 20.
Also, the armature 31 has an upper end that is elastically connected to the armature spring 33 installed in the case 10 to return to its original position from the position at which the armature 31 is spaced apart from the magnet 20.
Here, non-explained reference numeral “31a” denotes a rotation shaft of the armature 31, and reference numeral “34” denotes a support member to which an end of the spring 33 is connected.
Referring to FIG. 2, when the accident current that is significantly higher than the rated current flows through the heater 11, the magnet 20 may be excited to generate the magnetic attractive force.
Then, the armature 31 that is rotatably installed on a side of the magnet 20 rotates in a clockwise direction by using the support 32 as a rotation center to contact one surface of the magnet 20.
Simultaneously, the rotating armature 31 presses a lower end of the crossbar 51 that is disposed at the normal position. Then, the crossbar 51 is pushed by the rotating armature 31 to rotate in a counterclockwise direction.
Thus, since the crossbar 51 rotates from the normal position to the trip position, the instant trip operation may be realized.
The rotation of the armature 31 as described above may be stopped when the armature 31 contacts one surface of the magnet 20.
Thereafter, when the accident current is broken through the above-described instant trip operation, the armature 31 rotates to return to its original position by the elastic restoring force of the armature spring 33. Also, the contact between the armature 31 and the crossbar 51 is released, and the armature 31 rotates to return to the normal position by the elastic restoring force of the crossbar spring 52.
In the above-described operation, the armature 31 may rotate by the magnetic attractive force generated by the magnet 31 when the accident current occurs to physically contact the one surface of the magnet 31.
Generally, in this case, the accident current may flow along an arrow expressed as a dotted line through the heater 11 illustrated in FIG. 3.
However, when the rated current is less, and the heater 11 has high resistance, as illustrated in FIG. 4, the accident current may flow along the following path: the support 32->the armature 31->the magnet 20, which have resistance less than that of the heater 11.
When the accident current flow via the armature 31 and the magnet 20, which are in contact with each other, arc may be generated at the contact portion between the armature 31 and the magnet 20. Here, the arc generation portion may be fused.
Thus, the fused state between the armature 31 and the magnet 20 may be maintained, and also, the rotation operation of the crossbar 51 at the lower end of the armature 31 may be restricted so that the crossbar 51 does not return to the normal position.
When the crossbar 51 does not return to the normal position, the molded case circuit breaker may be continuously maintained in the trip state. Thus, after the accident current is removed, the molded case circuit breaker may not perform the normal instant trip operation.
There is Korean Patent Publication No. 10-2006-0101035 as the related prior document. An instant trip apparatus of a molded case circuit breaker is disclosed in Korean Paten Publication No. 10-2006-0101035.